Yes, I admit the Guardian guy is clearly bonkers and could certainly have chosen his words better but I guess he must be talking more about plants and trees rather than animal wildlife. Isn't he inferring that sheep grazing and the contiuned subsidies for hill sheep farmers to make that even slightly viable just continue to supress expansion of what would otherwise be naturally wooded mountains?
From digging about on wiki, apprently to be considered for World Heritage Status as a natural, rather than cultural, place, the following criterea have to be met:
* Contains superlative natural phenomena or areas of exceptional natural beauty and aesthetic importance
* Is an outstanding example representing major stages of Earth's history, including the record of life, significant on-going geological processes in the development of landforms, or significant geomorphic or physiographic features
* Is an outstanding example representing significant on-going ecological and biological processes in the evolution and development of terrestrial, fresh water, coastal and marine ecosystems, and communities of plants and animals
* Contains the most important and significant natural habitats for in-situ conservation of biological diversity, including those containing threatened species of outstanding universal value from the point of view of science or conservation
I guess an environment, no matter how beautiful or full of teaming wild animals, might struggle to meet those criterea if 60% of the land has made like it is through tree clearing (yonks ago) and sheep grazing?